1. Field of the Invention
The present invention relates to liquid crystal display devices. In particular, the present invention relates to a transmissive liquid crystal display device.
2. Description of the Related Art
Liquid crystal display devices are devices performing display by modulation of light with the use of liquid crystal materials whose alignment is controlled in accordance with applied voltage. Specifically, the liquid crystal display devices are roughly divided into two, depending on light used for display: external light such as natural light or interior lighting, or light emitted from light sources (backlights) included in the liquid crystal display devices itself. In general, the liquid crystal display devices which perform display with the use of the former are referred to as reflective liquid crystal display devices, and the liquid crystal display devices which perform display with the use of the latter are referred to as transmissive liquid crystal display devices. Note that the transmissive liquid crystal display devices can widely be used as devices in comparison with the reflective liquid crystal display device because the display quality varies depending on external environment (intensity of external light).
In general, transmissive liquid crystal display devices have display panels including a plurality of pixels arranged in matrix and backlights delivering white light to the display panels. Further, the pixel includes a transistor for controlling an input of an image signal, a liquid crystal element to which voltage corresponding to the image signal is applied, a color filter that transmits only light with a wavelength of a given color (e.g., red (R), green (G), or blue (B)). Note that the liquid crystal element includes a pair of electrodes and a liquid crystal material provided between the pair of electrodes. In addition, the transmittance of white light is controlled for each pixel and only light with a wavelength of a given color is transmitted by a color filter, so that display of each pixel is determined. Therefore, an image is displayed on the display panel included in the liquid crystal display device.
In recent years, there has been a growing interest in global environment, and the development of liquid crystal display devices consuming less power has attracted attention. For example, Patent Document 1 discloses a technique by which power consumption of a liquid crystal display device is reduced. Specifically, Patent Document 1 discloses a liquid crystal display device in which all data signal lines are electrically separated from a data signal driver to be in an indefinite state (also referred to as a floating state) during an idle period in which all scan lines and data signal lines are in a non-selected state.